Queesy, thanks for asking that question. I needed that function too. However, the author page now shows the result twice 🙁 I assume it is because the author has two posts with different categories attached to them!?

true, it is inside the loop and I could place it outside to make it work. The template, Xplosive, has some kind of blue shading at the top of every template, which will go missing then. So maybe the question is how to keep that – I do not know what is controlling the shading. Style.css perhaps?